Follow up cleanup of some unit tests for right click handling.

[gaaclarke]

Some cleanup after an external contribution: #27019

Removed conditional compilation which makes it easier to maintain until we transition to xcode 13 and it makes the steps for removal more apparent and easier to track.

cc @moffatman

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[jmagman]

I am trying to get a frankenstein Xcode bundle package on the engine builders. It's Xcode 12.0 + SDKs/runtimes for iOS 13, iOS 13.5, iOS 14, and iOS 15 beta 2. So it's @available(iOS 15, *) but the XCTest framework is from Xcode 12. Once the tests are running in a different builder than the framework builds after the recipe refactor, we can switch it to the opposite where it's Xcode 13 beta 2 + older iOS SDKs and runtimes.

Is the purpose of this change make sure it's running on iOS 15 AND has the Xcode 13 XCTest framework embedded?

Right now on Xcode 12.5 there are multiple warnings on this patch:

iPadGestureTests.m:34:45: Undeclared selector 'supportsPointerInteraction'
iPadGestureTests.m:69:21: Undeclared selector 'rightClick'
iPadGestureTests.m:73:16: PerformSelector may cause a leak because its selector is unknown

On Xcode 13 it has one warning:

iPadGestureTests.m:73:16: PerformSelector may cause a leak because its selector is unknown

[gaaclarke]

The warnings are expected. They aren't anything to be concerned about and will disappear after we have xcode 13, I can suppress them if you want. The purpose of the change is to make sure all the code is compiling. That way we can at least ensure the tests compile even if they don't run on CI. Also instead of creating a blanket conditional compilation this has fine grain information about what is being used from the newer SDK and links an issue for its removal when CI is capable and notes the condition whence it can be removed.

edit: (also it executes when it can =)

[jmagman]

Hopefully we can get rid of all this reflection soon...